At the moment, nearly all model-based scenarios that limit global warming to 2 °C or less use negative CO2 emission technologies (NETs), particularly bio-energy with carbon capture and storage (BECCS). Still, investments in these technologies continue to be relatively small, and concerns are being raised regarding the large-scale application of such technologies. If no explicit policy decisions are taken soon, however, it will not be possible to meet the climate targets of the Paris Agreement without the use of NETs. Therefore, as part of the discussion on strengthening current climate policies, policymakers and other stakeholders will have to address the role of NETs, in order to make an informed decision on post-2050 pathways.

Negative emission technologies include bio-energy with carbon capture and storage, but also afforestation. A closer look at the scenarios in the Intergovernmental Panel on Climate Change (IPCC) database that are likely to limit global warming to 2 °C or less reveals how important the implementation of NETs is for the timing of mitigation efforts. Scenarios with net-negative CO2 emissions require a 40% to 60% reduction in all greenhouse gas emissions, globally, by 2050, relative to 2010 levels. However, the few scenarios in the IPCC database that do not include net-negative CO2 emissions require a much larger global reduction by 2050, namely in the range of 60% to 75%. Nevertheless, BECCS and other negative CO2 emission technologies have been criticised — among other things, for their possible impact on sustainability issues (e.g. land use), and arguably for their speculative nature. Moreover, at the moment, societal support for these technologies is low. For instance, in recent years, several scheduled projects using CCS were cancelled because broad political support was lacking or due to societal opposition.

In a recent article in Nature Energy, PBL researchers argue that policymakers and stakeholders should explicitly discuss the role of NETs, in order to arrive at a timely, informed and conscious decision on post-2050 pathways. As part of this discussion, it is important to realise that, even when including NETs, rapid near-term emission reductions are needed (beyond those currently pledged in international negotiations). At the same time, it is also important to realise that it is really difficult to achieve the Paris climate targets without using NETs. The amount of NETs and type of technology used, however, is more flexible. The discussion on this issue, therefore could help provide clarity for near-term energy decisions and investments.

If decision-makers come to the conclusion that a reliance on NETs should be limited (or even be avoided), emission reductions will need to be closer to the upper limit of the mitigation range given by the IPCC. If, in contrast, NETs were to be applied extensively, it would help to define the criteria under which they are considered acceptable, and as a result also which types of NET technologies. Moreover, it would also be important that more experience is gained in these technologies and investment in research and development is started as soon as possible.